I made eye contact with the person sitting diagonally across from me.
The shop is diagonally across the intersection.
Usually written in kana; the kanji forms 斜交い and はす交い are rare.
Rare kanji spelling; the kana form is strongly preferred.
Mixed kanji-kana spelling; very rare.
The origin is uncertain. It may be related to 斜 (はす, 'diagonal') and 交い (かい, 'crossing'), but the exact derivation is unclear.